Affected Software and Vulnerability Severity Ratings

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the Aug bulletin summary.

[1]This update is only available via [Windows Update](http://go.microsoft.com/fwlink/?linkid=21130).

[2]Windows 10 updates are cumulative. The monthly security release includes all security fixes for vulnerabilities that affect Windows 10, in addition to non-security updates. The updates are available via the Microsoft Update Catalog.

*The Updates Replaced column shows only the latest update in any chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is provided on the Package Details tab).

Note The vulnerability discussed in this bulletin affects Windows Server 2016 Technical Preview 5. To be protected from the vulnerability, Microsoft recommends that customers running this operating system apply the current update, which is available from Windows Update.

Vulnerability Information

Secure Boot Security Feature Bypass Vulnerability – CVE-2016-3320

A security feature bypass vulnerability exists when Windows Secure Boot improperly loads a boot manager that is affected by the vulnerability. An attacker who successfully exploited this vulnerability could disable code integrity checks, allowing test-signed executables and drivers to be loaded onto a target device. Furthermore, the attacker could bypass Secure Boot Integrity Validation for BitLocker and Device Encryption security features.

To exploit the vulnerability, an attacker who has gained administrative privileges or who has physical access to a target device could install an affected boot manager.The security update addresses the vulnerability by blacklisting affected boot managers.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list: